To the Editor.—Dr Bresee et al1 reported an epidemic of HCV infection among immunodeficient persons treated with Gammagard intravenous immune globulin (IGIV). The aggregate of 23 cases in 1 clinic was convincingly attributed to 9 or more lots. Related cases are known elsewhere in the United States, as well as in the United Kingdom, Sweden, and Spain. Investigators of the Boston, Mass, aspect of the epidemic concluded that the introduction of more sensitive donor screening for the antibody to HCV (anti-HCV) resulted in increased amounts of uncomplexed virus entering the IGIV fraction.2 However, other factors may have been equally or more important for this product.The HCV cases in 1983 associated with Gammagard from a pilot plant3 provoked only a brief postmarketing surveillance study, interpreted as showing safety. The subsequent absence of reported cases until 1994 associated with any US Gammagard IGIV preparation does not mean that none occurred.